Submitted to: American Society of Plant Physiologists Meeting
Publication Type: Abstract Only
Publication Acceptance Date: July 24, 2000
Publication Date: July 24, 2000
Technical Abstract: Pyrithiobac efficacy evaluated over two growing seasons on the Texas High Plains was correlated with air temperature at the time of application (R2 = 0.90). Observed weed control (>90%) resulted in a recommendation that postemergence pyrithiobac applications be made when air temperatures are between 20 and 34 C. However, the potential utility of this recommendation to producers has not been examined. The objectives of this study were to determine the probability, frequency, and duration of the temperature-based pyrithiobac application range, investigate the utility of using computer visualization to convey the significance of pyrithiobac efficacy thermal dependence, and examine the impact of the application recommendation in other regions. On the Texas High Plains, the recommended temperature range occurred during 59 to 93% of the daylight hours. Therefore, up to 41% of pyrithiobac applications may result in poor weed control. In some years, the temperature exceeded 34 C on more than half the days evaluated for mor than 6 hours. However, the duration of temperatures below 20 C was generally less than 2 hours. Three-dimensional computer images of seasonal temperature data with a color overlay corresponding to temperatures below, within, and above the recommended range were developed. The impact of the recommended application range may be minimal in North Carolina and Mississippi where more than 80% of the daylight hours were within range in each of three seasons evaluated. In arid Arizona and Oklahoma, the application range occurred during less than 60% of the daylight hours in every year evaluated. Therefore, the probability of achieving good weed control with pyrithiobac may be enhanced if applications are made when air temperatures are between 20 and 34 C.